It's difficult to grade the coaches when looking at it from the outside, because I'm just not privy to a lot of stuff that would be very useful to know.
But I would say this:
This was a 6-10 football team last year that traded away its best offensive player, traded away its best (in my opinion) cornerback on the eve of the season, and of course I have to look at what the coaching staff had to work with on the whole while evaluating their work.
Joe Philbin and crew were forced to work with a bad offensive line, a bad receiving corps, a lack of athleticism at the tight end position, a lack of pass rushers, and a lot of poor or underdeveloped players in the secondary. Faced with this, Joe still decided to start his rookie QB and get the growing pains out of the way now and set the team up for accelerated success in 2013 and beyond. Several cornerbacks were lost due to injury and the team wound up starting players at WR and CB who were picked up off the street the same week at one point. They still improved the team's record.
Look at the injuries. Long, Marshall, Carroll, Bess, Clay, Thomas all lost for the year. Burnett and Dansby were suffering from real injuries for almost the entire season. Tannehill played several games hurt. Hartline nearly died in the offseason, missed training camp, and then got hurt late in the year. I mean, these guys aren't even star players to begin with (my feelings on Jake Long well known by this point) and almost everyone agreed that this team had awful depth.
So, to keep it simple, this staff inherited a 6-10 team (3 straight losing seasons) that had just lost its best receiver and cornerback, started a rookie QB with the future in mind, lost key players due to injury down the stretch, and still improved the team's record, beating two playoff teams along the way.
I would give Joe Philbin a B at minimum for having the courage and foresight to start Ryan Tannehill. All things considered, I give the staff an A. Yes, the team's record was 7-9, but the fact is that I gave the team's General Manager a grade of F for the previous four years during which this hole was dug. Again, you take a 6-10 football team, put six games against playoff teams on the schedule, remove the best offensive player, put your new best receiver in the hospital on the brink of death during training camp, trade your best cornerback, the guy you sign to replace him gets hurt early and misses most of the season, and one of two Pro Bowl players on your roster gets hurt in training camp and stinks up the joint before going on IR late. And you improve the team's record by a game.
The coaching staff could not make chicken salad out of chicken ****, but at least they started cleaning up the mess.